PIN does not support special characters

[deyhle]

When having a PIN with special characters (e.g. German Umlauts äüö), which is normally allowed by the Banks, the connection fails (Error: "Nachricht enthält Fehler", tested with DKB). After changing the PIN to an ascii-alphanumeric one, it works.

[jostang]

I had the same problem. My pull request #40 fixes it.